1. Field of the Invention
The present invention relates generally to an air induction system for an engine, and more particularly to an improved air induction system for an engine that needs a relatively long intake passage.
2. Description of Related Art
An internal combustion engine typically comprises an air induction system with which air is introduced into one or more combustion chambers of the engine. Typically, the induction system includes a plenum chamber unit and one or more intake conduits. The plenum chamber unit is used to coordinate or smooth the airflow to the combustion chambers and to reduce noise in the induction system. The intake conduits generally extend between the plenum chamber and the combustion chambers to supply air in the plenum chamber to the combustion chambers. The intake conduits, however, not only connect the plenum chamber with the combustion chambers but also used to obtain the desired engine torque curve. Particularly, the length of the intake conduits is one of principal elements to determine the engine torque. In general, if a relatively long conduit is applied, the engine torque can be improved in a range of low and/or middle engine speed. If a relatively short conduit is employed, the engine torque can be improved in a range of high engine speed.
Engines that need the long intake conduit(s) for improved low and middle range torques can pose a difficult problem. For instance, a typical engine for an outboard motor is surrounded by a protective cowling. Space for the long intake conduit(s) is thus extremely limited. Enlarging the protective cowling to make a roomier space is not an acceptable option since outboard motors are required to be as compact as possible for carriage and storage. Increasing the number of parts to form the conduits and unit is also not acceptable since a large number of parts will increase the assembly work and thus the cost of producing the engine.
Engines constructed in accordance with the preferred embodiments of the invention provide an improved air induction system having a relatively long intake conduit without requiring a roomier space around the engine. These engines do not require a large number of parts or pieces to form the conduits and unit. Rather, they decrease the number of parts that forms the system.
A significant feature of the preferred embodiments is an induction system of extended length that does not require any increase in size to the engine cowling. As a result, these preferred embodiments have improved low and middle range torques.
In accordance with one preferred embodiment of the invention, the air induction system includes a plenum chamber remote from the combustion chamber and connected to the combustion chamber by an intake conduit. In addition, the air induction system includes an additional air inlet conduit extending between an inlet within the protective cowling and the plenum chamber. A significant feature of this preferred embodiment is that this inlet conduit effectively lengthens the intake conduit without impinging upon the limited space within the cowling. Rather, this inlet conduit extends along and between an extended length of the intake conduit.
As a result, improved low and middle range torques are achieved without sacrificing the advantages of a compact engine cowling.
Another feature of the preferred embodiment is that a minimum number of parts are required to assemble the air induction system. Thus, the plenum chamber, the intake conduits between the combustion chamber and plenum chamber, and the inlet conduits between the air space within the cowling and the plenum chamber are substantially provided by two formed plastic members.
One preferred embodiment of the air induction system described is configured for an engine having two cylinder banks, one of which is disposed on the port side of the engine and the other disposed on the starboard side. Two air induction systems, are used to supply air to the two cylinder banks with the plenum chambers of one system closely disposed to the plenum chamber of the other system in front of the engine crankshaft member. A series of side-by-side inlet conduits and intake conduits are respectively coupled to the plenum chambers. As further described below, the two plenum chambers are advantageously connected by air pressure balancer hoses.
Another feature of the preferred embodiments is improved air induction system for an engine that can effectively reduce noise.
An additional aspect of the preferred embodiments of the air induction system is that the flow of air is reversed within the plenum chamber so that the air flowing into the inlet conduit flows in the opposite direction of air flowing from the plenum chamber to the engine""s combustion chamber.
In accordance with one aspect of a preferred embodiment of the present invention, an internal combustion engine comprises an engine body and an air induction system enclosed in a protective cowling. The engine body includes a cylinder block defining at least one cylinder bore. A piston is reciprocally disposed within the cylinder bore. A cylinder head member closes the respective cylinder bores to define a combustion chamber together with the cylinder bore and the piston. The air induction system is arranged to supply air to the combustion chamber. The air induction system includes an intake conduit communicating with the combustion chamber. An inlet conduit communicates with the intake conduit and, at least in part, extends along the intake conduit.
In accordance with another aspect of a preferred embodiment of the present invention, an internal combustion engine comprises an engine body and an air induction system. The engine body includes a cylinder block defining at least two cylinder bores. Pistons are reciprocally disposed within the respective cylinder bores. A cylinder head member closes each one of the respective cylinder bores to define at least two combustion chambers together with the cylinder bores and the pistons. The air induction system is arranged to supply air to the combustion chambers. The air induction system includes at least two intake conduits communicating with the combustion chambers. An inlet conduit communicates with both of the intake conduits. The inlet conduit, at least in part, extends along the intake conduits.
In accordance with a further aspect of a preferred embodiment of the present invention, an internal combustion engine comprises an engine body. A moveable member is moveable relative to the engine body. The engine body and the moveable member together define a combustion chamber. An air induction system is arranged to supply air to the combustion chamber. The air induction system includes an intake conduit communicating with the combustion chamber. A plenum chamber member defines a plenum chamber located upstream of the intake conduit. An inlet conduit communicates with the plenum chamber to introduce the air into the plenum chamber. The inlet conduit, at least in part, is unitarily formed with the intake conduit.
In accordance with a still further aspect of a preferred embodiment of the present invention, an internal combustion engine comprises an engine body. At least two moveable members are moveable relative to the engine body. The engine body and the moveable members together define at least two combustion chambers. An air induction system is arranged to supply air to the combustion chambers. The air induction system includes first and second intake conduits communicating with the combustion chambers. The first intake conduit extends on a first side of the engine body. The second intake conduit extends on a second side of the engine body. The second side is located generally oppositely to the first side relative to the engine body. At least one plenum chamber member defines a plenum chamber located upstream of the first and second intake conduits. First and second inlet conduits communicate with the plenum chamber. The first inlet conduit, at least in part, extends generally along the first intake conduit. The second inlet conduit at least in part extends generally along the second intake conduit.
In accordance with a yet further aspect of a preferred embodiment of the present invention, an internal combustion engine comprises an engine body. A moveable member is moveable relative to the engine body. The engine body and the moveable member together define a combustion chamber. An air induction system is arranged to supply air to the combustion chamber. The air induction system includes an intake conduit communicating with the combustion chamber. A plenum chamber member defines a plenum chamber located upstream of the intake conduit. An inlet conduit communicates with the plenum chamber to introduce the air into the plenum chamber. The inlet conduit, at least in part, extends generally along the intake conduit.
In accordance with a further aspect of a preferred embodiment of the present invention, an outboard motor comprises a drive unit and a bracket assembly adapted to be mounted on an associated watercraft to support the drive unit. The drive unit includes an internal combustion engine. The engine comprises an engine body. A moveable member is moveable relative to the engine body. The engine body and the moveable member together define a combustion chamber. An air induction system is arranged to supply air to the combustion chamber. The air induction system includes an intake conduit communicating with the combustion chamber. A plenum chamber member defines a plenum chamber located upstream of the intake conduit. An inlet conduit communicates with the plenum chamber to introduce the air into the plenum chamber. The inlet conduit has an opening positioned opposite to the bracket assembly relative to the plenum chamber member.